1. Field of Invention
The present invention relates to a method of manufacturing a microlens which constitutes, for example, a microlens array plate suited for application to an electrooptic device, such as a liquid crystal device. The invention further relates to a microlens manufactured by the manufacturing method, a microlens array plate, an electrooptic device including the microlens, and an electronic equipment including the electrooptic device.
2. Description of Related Art
In a related art electrooptic device, such as a liquid crystal device, various wiring lines, such as data lines, scanning lines and capacitance lines, and various electronic elements, such as thin film transistors (hereinbelow “TFTs”) or thin film diodes (hereinbelow “TFDs”), are formed within an image display area. In each pixel, therefore, a region through or from which light capable of actually contributing to display is transmitted or reflected is essentially limited due to the existence of the various wiring lines and electronic elements, etc. Specifically, regarding each pixel, the opening rate of each pixel as is the rate of a region through or from which light actually contributing to display is transmitted or reflected (that is, the aperture region of each pixel), to the whole region, is about 70%, for example. Illumination source light or external light which is entered into the electrooptic device mostly includes parallel light rays, at least, when passing through an electrooptic substance layer, such as a liquid crystal layer, within the electrooptic device. However, in a case where parallel light rays have been entered into the electrooptic device, only that part of the whole quantity of light which is proportional to the opening rate of each pixel can be utilized without any contrivance.
Therefore, in the related art, a microlens array which includes microlenses corresponding to the respective pixels can be formed in an opposite substrate, or a microlens array plate can be stuck on an opposite substrate. Due to such microlenses, light rays which ought to progress toward the non-aperture regions of the respective pixels except the aperture regions thereof without the microlenses are collected in pixel units, so as to be guided into the aperture regions of the respective pixels when they are transmitted through the electrooptic substance layer. As a result, a bright display is realized by utilizing the microlens array in the electrooptic device.
The manufacture of this type of related art microlens is provided as stated below. First, a mask which is provided with a pit at a position corresponding to the center of the microlens to be formed is formed on, for example, a transparent substrate. Subsequently, the transparent substrate is subjected to wet etching through the mask, to thereby excavate a spherical recess which defines the curved surface of the microlens. Thereafter, the mask is removed, and the recess is filled up with a transparent medium of high refractivity. Thus, the microlens is formed in which a hemispherical recess centering around the pit having been first provided in the mask is included as a lens spherical surface. The microlens array can be manufactured by forming a large number of such microlenses in the shape of an array.
In the case of this type of microlens, it is important as basic requirements to enhance a lens efficiency and further to diminish spherical aberration.
According to the related art method of manufacturing the microlens as stated above, however, a non-spherical lens cannot be manufactured, although a spherical lens can be manufactured, comparatively easily.
In this regard, in order to manufacture the non-spherical lens, the related art includes a complicated and high-degree manufacturing method, for example, one in which a non-spherical recess is formed from a separate material on a substrate and is thereafter transferred onto the side of the substrate, or one in which a substrate is subjected to a plurality of different etching steps stage by stage. Such a manufacturing method, however, is basically difficult and increases manufacturing costs as well as reduces an available percentage. Further, there occurs the problem that, as manufacturing steps become complicated and high in degree, controlling the degree of non-sphericalness in the non-spherical lens becomes technically very difficult.